The present invention relates to a DC plasma display panel and more particularly to a DC plasma display panel having electrodes formed by plasma spray coating.
Electrodes for use in conventional DC plasma display panels (hereinafter referred to as "DC--PDP's") have been produced, for example, by forming an about 75 to 100.mu. thick layer of an alloy of Fe and Ni, an alloy of Fe, Ni and Cr (e.g., a 42-6 alloy) or the like by etching, electroless plating, electroplating, deposition, or by printing using a thick film printing technique on an insulative substrate such as a glass plate or a ceramic plate. These conventional electrode-producing methods, however, have a number of disadvantages. For example, with an electrode produced by etching, registration problems arise which creates difficulties in assembling a panel because the number of parts is large. Moreover, electrodes produced by the other methods are poor in bonding among metal particles. In particular, electrodes produced by deposition or plating are poor in durability because such methods can not produce electrodes of sufficient thickness.
Hereinafter, a prior art plasma display panel will be explained in detail with reference to FIGS. 1A and 1B of the accompanying drawings. Referring to FIG. 1A, the prior art plasma display panel includes a front glass plate 1, an electrode (anode) 2 provided on the inner surface of the front glass plate 1, a spacer 3 forming discharge cells 4, a rear glass plate 5, and an electrode (cathode) 6 provided on the inner surface of the rear glass plate 5. The cathode 6 is provided in a layer form using procedures such as thick film printing using a Ni paste, deposition, or plating. The electrode provided by such procedures suffers from the problem that the bonding among metal particles is poor. Furthermore, the electrode provided by thick film printing has the disadvantage that its physical strength is poor, and the electrodes provided by deposition, plating, etc. have the disadvantage that their durability as a cathode is poor because the thickness thereof is limited.
A plasma display panel as illustrated in FIG. 1B includes a front glass plate 1, a cathode 6 in the form of a ribbon, a spacer 3 forming discharge cells 4, a rear glass plate 5, and a linear anode 2 disposed on the rear glass plate 5. In order to provide a sufficient durability, the cathode 6 is produced in the form of a ribbon from a metal plate, such as a 42-6 alloy plate, having a thickness of about 75.mu. using an etching technique. This method, however as described hereinbefore, has the disadvantage that registration creates difficulties in assembling a panel because the number of parts is large.
Electrode materials such as Fe, Ni and Cr which have heretofore been used have work functions of about 4.5 eV which is relatively large for use as a cathode for DC-PDP's. Moreover, these materials required relatively high operating voltages of about 300 V. An operating voltage of this magnitude makes the power consumption of a DC-PDP correspondingly high.
In order to reduce this power consumption, it has been proposed to use substances having small work functions as electrode materials. Of such materials, hexaborides of rare earth elements (e.g., LaB.sub.6 and CeB.sub.6) have the following characteristics:
(a) The work function is small, for example, 2.7 eV for LaB.sub.6.
(b) The melting point is high, for example, 2600.degree. C. for LaB.sub.6.
(c) The electrical conductivity is good.
(d) There is little abrasion due to ion impact.
Of these characteristics, (a) the low work function, (c) the good electric conductivity, and (d) the small amount of abrasion from ion impact are desirable properties for a cathode material. However, it is very difficult to deposit a hexaboride of a rare earth element on a cathode substrate of DC-PDP because of (b) the high melting point. For example, where the hexaboride is converted into the form of an ink and coated on an electrode substrate with a usual printing method, the adhesive force is low because of the very high melting point and sintering temperature of the hexaboride and hence firm adhesion cannot be obtained. Addition of a binder may deteriorate the discharge characteristics. Furthermore, with a DC-PDP having a regular structure, high temperature heat processing may result in deformation of the panel. For these reasons, high melting point materials have not been used in practice for electrode materials.